Thermal expansion means for maintaining and adjusting cutter knife clearance



w 3 m m% A M H m m E E B mm 0 M d N W TH D WF June 1, 1965 THERMALEXPANSION MEANS FOR MAINTAINING AND ADJUSTING 90 mm Vm mm: m mOP O n Z mm I a B Q h M m m L I 8 9v 5.30528 5 30528 hv w W A X? 5v ww 40v mu. w:ESE EH55 Turn: TQM. N MW rm 6m 3w M k a wmfiw 3% nut m Y Q wm Qon B E Rmm m\ E mw QOO00000 mv MN Nv Q Q mm mm mm i 1 mm & \v I a 3 Q t v S S Evw A ml 4 mm H E Ebb AGENT United States Patent 3,186,275 THERMALEXPANSION MEANS FOR MAINTAIN- gi GCEAND ADJUSTING CUTTER KNIFE CLEAR-This invention relates to the cutting of web material into sheets, andmore particularly, it relates to rotary web cutting apparatus equippedwith means for thermally controlling the expansion of the pedestals ofthe cutting apparatus and, thereby, controlling the clearance betweenthe cutting knives.

With most rotary web cutters, difficulties are encountered when startingthe cutter after an appreciable down time in that the cutting knivestend to hit or pound very heavily. The pounding of the knives graduallydecreases as running of the cutter continues, until cutting actionbecomes normal after several hours of continued operation. The heavypounding during start-up often damages the cutting edges of the knives.If the knives are adjusted at start-up to reduce the pounding andprolong the life of the knives, proper cutting can not be achieved afterthe cutter has run for several hours. It has been felt in the past thatthe pounding effect was due to the fact that the knives or the cutterdrum had not yet warmed up. In reality, if such warming of the knives ordrum did occur, the knife clearance would actually decrease and poundingof the knives would increase due to thermal expansion of the knives orthe drum. However, this explanation has been accepted for many years inthe web cutting field, with little effort being expended on defining thereal problem.

It has now been discovered that the real problem in this area is thatthe pedestals supporting the cutter drum, and the bearings associatedtherewith, are warmed by heat created in the bearings due to therotation of the cutter drum. The pedestals, being warmed, expand inlength as cutting continues until an equilibrium heat exchange obtains,at which time the pounding of the cutting knives no longer exists sinceexpansion of the pedestals increases the clearance between the knives.This also explains why, if at start-up the knives are adjusted to avoidpounding, poor cutting results in a few hours running time, since theclearance between the knives increases beyond proper cutting clearancedue to the thermal expansion of the cutter pedestals. No one before hasdefined the real problem, and, therefore, an improved rotary web cutterdesigned to compensate for this phenomenon has not been previouslydisclosed.

On the basis of the above discovery, heating means were mounted on thecutter pedestals, and a temperature sens ing device was installed ineach cutter pedestal. The pedestals were quickly heated by the heatingmeans to a suitable selected temperature before start-up of the cutter,and the selected temperature of the pedestals was controlled by means oftemperature controllers. By coI1- trolling the temperature of thepedestals, and thus the thermal expansion of the pedestals, properclearance between the cutting knives was maintained, and criticalchanges in the clearance between the cutting knives were effected merelyby altering the temperature of the pedestals.

The invention will be best understood by reference to the followingdetailed description and drawing forming part of this specification inwhich:

FIGURE 1 is an elevational view of a rotary web cutter in which thepedestals of the cutter are equipped with heat producing and temperaturesensing means;

3,135,275 Patented June 1, 1965 FIGURE 2 is a side view of FIGURE 1showing heat producing means on a cutter pedestal and showing a type oftemperature controlling means;

FIGURE 3 is a block diagram illustrating the arrangement of the heatproducing, temperature sensing, and control means.

Referring to FIGURE 1, rotary cutter drum 10 is carried on journals 12,and drum 10 turns through one complete revolution for each cuttingoperation performed. Drum 10 is driven by any suitable means, usually bymechanical linkage to a drive motor (not shown). Journals 12 aresupported in suitable bearings 14 carried on front pedestal 16 and backpedestal 17. Pedestals 16 and 17 are mounted on the bed knife supportframes 18 by means of screws 20, and the bed knife support frames 18'are suitably mounted on the machine frame 19. A guard 22 is usuallyprovided between pedestal extensions 23 and 24. A blade or fly knife 26is suitably housed within a notch in the cutter drum 10 (as by means ofclamping screws not shown.) Stationary blade or bed knife 28 is mountedon the bed knife support 18 by means 32, and the bed knife 28 isadjustable toward and away from the fly knife 26 by means of adjustingscrews 34. In the main, the above cutting apparatus is of conventionalconstruction, and it can be seen that the pedestals 16 and 17 serve asthe supporting structures for the rotatable carrier (drum 19) of the flyknife 26.

Each of the cutter pedestals 16 and 17 is equipped with heating means,as for example electrical strip heaters 35, 36, 37, and 38. Preferably,one such heater is mounted on each of two opposite sides of eachpedestal 16 and 17 by means of screws 39 (FIGURE 2). In some instances,one heater on each pedestal may be sufficient, and more than two suchheaters on each pedestal may be employed. Appropriate shields areprovided over each such heater, as for example shield 35a associatedwith heater 35. Each of the cutter pedestals 16 and 17 is equipped withtemperature sensing means, as for example temperature sensing bulbs 4t)and 41. A temperature sensing bulb is installed in each pedestalpreferably by boring a hole into each pedestal and placing a temperaturesensing bulb into each hole. Electrical conduits 42 and 43 connect thestrip heaters 35 and 36, respectively, to a temperature controller 45mounted on the bed knife support 18 at the front side of the cutter, andtemperature sensing bulb 40 is connected to the temperature controller45 by means of electrical conduit 44. Electrical conduits 46 and 47connect the strip heaters 37 and 38, respectively, to a temperaturecontroller 45 mounted on the bed knife support 18 at the back side ofthe cutter, and temperature sensing bulb 41 is connected to thetemperature controller 49 by means of electrical conduit 48. Temperaturecontrollers 45 and 49 are connected by means of electrical conduits 50and 51, respectively, to a temperature indicator unit 52.

When the cutter is to be started, the indicator unit 52 is supplied withelectrical power which is transmitted by means of conduits 50 and 51,temperature controllers 45 and 49, and conduits 42, 43, 46 and 47 to thestrip heaters 35, 36, 37 and 38 associated with pedestals 16 and 17. Thepedestals 16 and 1'] are heated to some selected temperature above roomor ambient temperature and above the maximum temperature normallyreached by the pedestals due to heat transferred from the bearings 14.It has been found that with the equipment employed, a temperature ofabout F., as indicated by the temperature sensing bulbs 40 and 41, is asuitable temperature for the pedestals. This set temperature ismaintained by the temperature controllers 45 and 49, which supplyelectrical energy to the strip heaters 35, 36, 37, and 38 when necessaryin response to temperature changes indicated by the temperature sensingbulbs 40 and 41, to maintain the desired temperature of each pedestal.employed, the pedestals 16 and 17 are quickly brought to the desiredtemperature. Cutter knife clearance can then be mechanically adjusted,if necessary, before the cutter is started, and due to the substantiallyconstant temperature maintained at the cutter pedestals, the clearancebetween the fly knife 26 and the bed knife 28 Will remain constant underany and all operating conditions.

Conventional electrical strip heaters, temperature controllers, sensingelements and indicator unit have been employed. For example, suitableequipment is marketed as follows under the respective tradedesignations: resistance-type Chromalox PT Strip Heaters, 150 Watts, 120V.A.C., manufactured and marketed by Edwin L. Wiegand Co., and describedin the manufacturers catalog No. 60; Fenwal No. 53602-1 TemperatureController (potentiometer), using a thermistor sensing element FenwalNo. 74202-166, and the circuitry associated therewith, and Fenwal No.580022 Indicator Unit, which is a milliammeter with appropriate selectorswitches, manufactured by Fenwal Inc., and described in themanufacturers Bulletin MC-190. This equipment permits very precisecontrol of the temperature of the pedestals. It has been noted that achange of 2 F. in the pedestal temperature may effect a change in knifeclearance of .0001 of an inch, which in many cases will be thedifference between cutting or not cutting completely a traveling webpassing between the cutting knives.

The indicator unit 52 referred to above and shown in FIGURE 2 has acenter knob 54 which permits selection of the front or back pedestaltemperature for display. By pressing and holding the push button 56, theset temperature for a pedestal is displayed on scale 58. The temperaturedesired is roughly set by means of calibrated knobs 6t) and 62, knob 60being associated with the front pedestal 16, knob 62 being associatedwith the back pedestal 17, and a precise temperature is set (as forexample for the front pedestal 16) by holding down button 56 andadjusting knob 60 until the desired temperature is displayed on scale58.

It was noted that when the speed of the cutter changed or was changed toaccommodate a different basis weight of paper, knife adjustment wasnecessary in order to obtain a clean cut through the traveling Web. Ifmachine speed was increased, the bearings 14 created additional heatcausing the pedestals to expand, thus effecting a change in knifeclearance. However, by means of the present invention, a pedestaltemperature can be set above the maximum temperature brought about byhearing heatup, and increases in machine speed will have no effect onthe knife clearance. Thus, the pedestal heaters not only find utility inovercoming the pounding of the cutting knives at the beginning of a run,and thereby prolong the life of the knives, but they compensate forchanges in the speed of the cutter, maintaining optimum knife clearanceunder all operating conditions. Further, critical changes in knifeclearance can be made by merely raising or lowering the set temperatureof the pedestals, thereby changing the knife clearance as the pedestalsexpand or contra-ct and obviating the mechanical readjustment of theknife clearance.

Obviously, means for cooling rather than heating the pedestals may beemployed for maintaining the pedestals at the desired constanttemperature. Such means as water jackets, associated with the pedestals,through which cold water or other cold fluids are circulated, or directcooling by means of cool air blasts directed against the pedestals, orthermoelectric cooling, may be employed.

For reasons of simplicity, a web cutting mechanism employing a rotatingfly knife and stationary bed knife has been described. However, meansfor thermal expansion control, as described herein, could be applied toWeb cutting mechanisms in which both the fly knife and the bed knife arerotated.

The thermal expansion phenomenon, and the means for controlling the sameas disclosed in this patent, can have With the equipment applicationswith other paper manufacturing and converting machinery such as in bagmaking machines, box making machines, textile machines, metal workingmachines, etc. Where the maintenance of very precise clearance betweenelements of the machines is required.

While a preferred embodiment of the invention has been illustrated anddescribed in detail, it is to be understood that changes may be madetherein and the invention embodied in other structures. Hence, thepresent embodiment is to be considered as illustrative and not asrestrictive, and it is intended to cover the invention in whatever formits principles may be utilized.

I claim:

1. A web cutting machine comprised of a bed knife, a rotary cutter drum,a fly knife carried in fixed position on the cutter drum and cooperatingwith said bed knife at a selected clearance therefrom to sever atraveling web passing between said bed knife and said fly knife,journals upon which said drum is carried, and pedestals supporting saidjournals; characterized in that heating means are mounted on saidpedestals for heating said pedestals above the normal maximumtemperature of the pedestals attained during running of the machine,temperature sensing means are mounted on said pedestals vfor measuringthe temperature of the pedestals, and control means are associated withthe heating means and temperature sensing means for activating saidheating means in response to temperature changes of the pedestalsindicated by said temperature sensing means, to maintain a selectedtemperature of the pedestals, and thereby maintain the selected cuttingclearance between the fly knife and the bed knife.

2. A web cutting machine comprised of a bed knife, a rotary cutter drum,a fly knife carried in fixed position on the cutter drum and cooperatingwith said bed knife at a selected knife clearance to sever a travelingweb passing between said bed knife and said fly knife, journals uponwhich said drum is carried, and pedestals supporting said journals;characterized in that at least one electrical strip heater is mounted oneach pedestal for heating each pedestal above the normal maximumtemperature attained by each pedestal during running of the machine, atemperature sensing bulb is mounted into the interior of each pedestal,and control means are associated with the electrical strip heaters andtemperature sensing bulbs, said control means responsive to changes inthe temperature of the pedestals as indicated by said temperaturesensing bulbs to activate said electrical strip heaters to heat thepedestals and thereby maintain a selected temperature of the pedestals,whereby the clearance between the fly knife and the bed knife ismaintained constant irrespective of machine speed and increased heatdeveloped therefrom.

3. In a rotary web cutting mechanism, in combination, a fly knife, arotatable carrier for said fly knife, supporting structures for saidrotatable fly knife carrier, heating means mounted on said supportingstructures for heating said supporting structures above the normalmaximum temperature of said supporting structures attained duringrunning of the web cutting mechanism, temperature sensing means mountedon said supporting structures for measuring the temperature of saidsupporting structures, and control means associated with the heatingmeans and temperature sensing means for activating said heating means inresponse to temperature changes of the supporting structures indicatedby said temperature sensing means, to maintain a selected temperature ofsaid supporting structures.

4. In a rotary web cutting mechanism, in combination, a fly knife, arotatable carrier for said fly knife, pedestals supporting saidrotatable fly knife carrier, at least one electrical strip heatermounted on each pedestal for heating each pedestal above the normalmaximum temperature attained by each pedestal during running of themachine, a temperature sensing bulb mounted into the interior of eachpedestal, and control means associated with the electrical strip heatersand temperature sensing bulbs, said control means responsive to changesin the temperature of the pedestals as indicated by said temperaturesensing bulbs to activate said electrical strip heaters and therebymaintain a selected temperature of said pedestals.

5. In a rotary web cutting mechanism, in combination, a bed knife, arotary cutter drum, a fly knife carried in fixed position on the cutterdrum and cooperating with said bed knife at a selected clearancetherefrom to sever a traveling Web passing between said bed knife andsaid fly knife, supporting structures for said rotary cutter drum, andtemperature varying means mounted on said supporting structures fornormally maintaining said supporting structures at a constanttemperature above the maximum temperature of the supporting structuresattained during running of the mechanism, and control means associatedwith the temperature varying means for activating said temperaturevarying means to vary the temperature of the supporting structures andthereby change dimensions of the supporting structures and effect :achange in the clearance between said fly knife and said bed knife.

6. In a rotary Web cutting mechanism, in combination, a bed knife, arotary cutter drum, a fly knife carried in fixed position on the cutterdrum and cooperating with said bed knife at a selected clearancetherefrom to sever a traveling web passing between said bed knife andsaid fly knife, pedestals supporting said rotary cutter drum, heatingmeans mounted on said pedestals for normally heating the pedestals to aconstant temperature above the maximum temperature of the pedestalsattained during running of the mechanism, and control means associatedwith the heating means for activating the heating means to further heatthe pedestals and thereby thermally expand the pedestals and effect achange in the clearance between said fiy knife and said bed knife.

References Cited by the Examiner UNITED STATES PATENTS 1,978,894 10/34Clark. 1,982,571 11/34 Clark. 2,271,637 2/42 Garrison 83171 X 2,621,73612/52 Scruggs 83-170 X 2,782,853 2/57 Hei'fe'lfinger 83-17O X 3,064,56311/62 Cook.

ANDREW R. JUHASZ, Primary Examiner.

1. A WEB CUTTING MACHINE COMPRISED OF A BED KNIFE, A ROTARY CUTTER DRUM,A FLY KNIFE CARRIED IN FIXED POSITION ON THE CUTTER DRUM AND COOPERATINGWITH SAID BED KNIFE AT A SELECTED CLEARANCE THEREFROM TO SEVER ATRAVELING WEB PASSING BETWEEN SAID BED KNIFE AND SAID FLY KNIFE,JOURNALS UPON WHICH SAID DRUM IS CARRIED, AND PEDESTALS SUPPORTING SAIDJOURNALS; CHARACTERIZED IN THAT HEATING MEANS ARE MOUNTED ON SAIDPEDESTALS FOR HEATING SAID PEDESTALS ABOVE THE NORMAL MAXIMUMTEMPERATURE OF THE PEDESTALS ATTAINED DURING RUNNING OF THE MACHINE,TEMPERATURE SENSING MEANS ARE MOUNTED ON SAID PEDESTALS FOR MEASURINGTHE TEMPERATURE OF THE PEDESTALS, AND CONTROL MEANS ARE ASSOCIATED WITHTHE HEATING MEANS AND TEMPERATURE SENSING MEANS FOR ACTIVATING SAIDHEATING MEANS IN RESPONSE TO TEMPERATURE CHANGES OF THE PEDESTALS